1. Field of Invention
The current invention relates generally to apparatus, systems and methods for the transmission and reception of electromagnetic waves. More particularly, the apparatus systems and methods transmit and receive electromagnetic waves with an array of antennas. Specifically, the apparatus, systems and methods provide for transmitting or receiving electromagnetic waves based on signals combined coherently by the planar tri-mode cavity.
2. Description of Related Art
Beamforming is a signal processing technique used in sensor arrays for directional signal transmission or reception. Circular array systems are generally comprised of three major parts: 1) the beamformer, 2) the commutator, and 3) a circular array of radiating antenna elements. Beamformers often include a power divider that splits the input power into portions that are sent to each element of the antenna array so that a beam is radiated. The radiated beam is shaped by the aperture distribution taper which is the amplitude and phase of the power going to each element of the array. In this invention a tri-mode cavity is used to shape the aperture distribution. In a circular array, beamforming takes advantage of illuminating an arc of sequentially arrayed elements that is centered about the direction of signal transmission or reception. The beamformer then controls the phase and relative amplitude of the signal at each antenna element, in order to create a pattern of constructive and destructive interference in the wavefront. When the beam needs to be steered in a different direction, this aperture distribution needs to be commutated to a different set of array elements that point in that direction. Assuming that each output port of the trimode cavity beamformer is pre-wired to each antenna element of the array, then the aperture distribution needs to be transferred to the new set of elements. By changing the phase of the inputs to the tri-mode cavity, the same aperture distribution can be produced at a different set of consecutive output ports that feed the appropriate antenna elements in the array.
Prior tri-mode cavity radio frequency power distribution systems, such as those disclosed by David Lerner in U.S. Pat. No. 4,005,379, generally functioned in the region of L-band (1.030 GHz) and contained a tri-mode cavity of a generally cylindrical shape with a multitude of standard SMA or T connectors located around the circumference. Tri-mode cavities are often large, heavy, and expensive to manufacture.
In order for beamformers to function at higher GHz values it is necessary to find an alternative to the previously bulky structures. Simply scaling down these bulky structures creates overlap amongst the multitude of probe connectors when the probe connectors are arranged in the more confined area. Additionally, this decrease in size required for the tri-mode cavity to function at higher GHz levels necessitates more rigorous tolerances, and these tolerances make previous designs prohibitively, expensive to manufacture. Therefore, there exists a need for a better power distribution cavity.